Any ideas for input?
I though I had it covered with this:

```` Ruby
assert_equal DateTime.new(2013,11,12,02,11), parser.call("2013-11-12T02:11Z")
assert_equal DateTime.new(2013,11,12,02,11), parser.call("2013-11-12T11:11+9")
````

And as such I think the code works as it should.